The present invention relates generally to a device construction used for tightening connecting bolts and, more particularly, to a device construction which is supported on the portion that is to be attached by the bolt and wherein the upper end of the connecting bolt of the device is provided with a gripping profile which corresponds to the profile of a coupling element such as a couple casing or coupling jaws also forming a portion of the device.
Connecting bolts are used for the attachment of lids onto pressure vessels such as, for example, reactor vessels, heat exchangers and steam generators as well as in jet engines. From German Pat. No. 1,300,467, it is known to provide the ends of such connecting bolts with a profile and the coupling jaws which are used to grip the ends of these connecting bolts have a corresponding profile so as to be able to seize and prestress the connecting bolts. The profile on the bolts is made by cutting uniform grooves with trapezoidal cross-sections into the neck of the connecting bolts as is done with anti-fatigue screws, and corresponding projections are provided on the coupling jaws which are adapted to engage with the grooves on the bolt.
However, the above construction for coupling bolts has the disadvantage that the profiled neck of the bolt and thus also the overall height of the coupling jaws must be relatively large since the stress distribution in the profiles of the neck and coupling jaws is unfavorable.